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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 145 records · Page 8Linked to original sources
USGS1992

The 1992 Landers earthquake and surface faulting

Faulting associated with the June 28, 992, earthquake near Landers, California, broke the surface of the ground over a length of more than 70 km, the longest surface rupture in the United States since the great San Francisco quake of 1906. the strongest shaking associated with this magnitude 7.6 (M S ) earthquake, the largest in the contiguous 48 states in the last 40 years, occurred in a sparsely populated sections of the Mojave Desert more than 200 km east of Los Angeles. the earthquake began with a sudden slip on the Johnson Valley fault about 10 km southwest of Landers. The initial fault movement probably occurred at a depth of less than 10 km. Surface faulting then propagated over 70 km to the north and northeast. The faulting linked preexisting faults-some previously known and mapped and others previously unknown-into a complex, coherent rupture zone.

California↗
USGS1987

Volcanic ash clouds; a continuing threat to international aviation

There was no warning. The British Airqays Boeing 747 was making its usual flight from Kuala Lumpur to Perth, Asutralia, that nihgt, late in June 1982. Altitude:12,000 metres (37,000 feet). Time about 23:00 UTC. Suddenly, an acrid odour began to pervade the aircraft, an eerie bluish glow lit up the edges of the wings, and in the cockpit the familiar hum of static started to break up the high-frequency communications. Then it happened.

Earthquakes & Volcanoes (USGS)↗
USGS1987

Seismological medals

Few studies have attempted to describe the large numbers of medals that have been struck to commemorate important seismological events. I was intrigued by these medals on the occasion of the transfer of the coin and medal collection from the Freiberg Military Academy to the special reserve of the University of Dresden. Seismic events are environmental events, so it is not surprising that mankind, in coming to terms with earthquakes, has tried to express his feelings about them in an artistic manner too. By understanding the topical importance of medals in seismological affairs, we can appreciate the hertiage of the past.

Earthquakes & Volcanoes (USGS)↗
USGS1993

Historic and prehistoric earthquakes near Klamath Falls, Oregon

Earthquakes have rocked the Klamath Falls in the past will continue to do so in the future. Scientists estimate the likelihood of future damaging earthquakes in an area by examining the area's past record of earthquakes and by evaluating the area's earthquake potential in relationship to its geologic setting. To supplement the historic catalog, which often covers only a short time span, they also attempt to identify prehistoric earthquakes preserved in the rocks and sediments of the area. The conclusion drawn from such studies in the Klamath Falls area is that earthquakes in the 4-6 magnitude range, which are capable of light to moderate damage, occur on the order of one or more every few decades. Even a major earthquake in the 7+ magnitude range cannot be ruled out at some future time. However, the area's historic record, which goes back only about 100 yrs, is too short to estimate the frequency of such large shocks. This article is a brief summary of the geologic setting and the historic and prehistoric record of earthquakes in Klamath Falls and the surrounding area.

Oregon↗
USGS1991

The intensities and magnitudes of volcanic eruptions

Ever since 1935, when C.F Richter devised the earthquake magnitude scale that bears his name, seismologists have been able to view energy release from earthquakes in a systematic and quantitative manner. The benefits have been obvious in terms of assessing seismic gaps and the spatial and temporal trends of earthquake energy release. A similar quantitative treatment of volcanic activity is of course equally desirable, both for gaining a further understanding of the physical principles of volcanic eruptions and for volcanic-hazard assessment. A systematic volcanologic data base would be of great value in evaluating such features as volcanic gaps, and regional and temporal trends in energy release.

Earthquakes & Volcanoes (USGS)↗
USGS1987

An interview with Bruce A. Bolt

Professor Bruce Bolt was educated in Australia and first came to the United States in 1960 on a Fulbright Fellowship to the Lamont Geological Observatory of Columbia University. In 1963 he was appointed Director of the Seismographic Stations at the University of California at Berkeley. In June 1988, he steps down as Director but his association will continue as Professor of Seismology. Henry Spall interviewed him again 10 years after a 977 interview published in the Earthquake Information Bulletin.

Earthquakes & Volcanoes (USGS)↗
USGS1989

Measuring the size of an earthquake

Earthquakes range broadly in size. A rock-burst in an Idaho silver mine may involve the fracture of 1 meter of rock; the 1965 Rat Island earthquake in the Aleutian arc involved a 650-kilometer length of the Earth's crust. Earthquakes can be even smaller and even larger. If an earthquake is felt or causes perceptible surface damage, then its intensity of shaking can be subjectively estimated. But many large earthquakes occur in oceanic areas or at great focal depths and are either simply not felt or their felt pattern does not really indicate their true size. Today, state-of-the-art seismic systems transmit data from the seismograph via telephone line and satellite directly to a central digital computer. A preliminary location, depth-of-focus, and magntidue can now be obtained within minutes of the onset of an earthquake. The only limiting factor is how long the seismic wave stake to travel from the epicenter to the stations-usually less than 10 minutes.

Earthquakes & Volcanoes (USGS)↗
USGS1990

National Earthquake Hazards Reduction Program; time to expand

All of us in earthquake engineering, seismology, and many related disciplines have been directly or indirectly affected by the National Earthquake Hazards Reduction Program (NEHRP). This program was the result of the Earthquake Hazards Reduction Act of 1977 (Public Law 95-124). With well over a decade of experience, should this expression of public policy now take a different or expanded role?

Earthquakes & Volcanoes (USGS)↗
USGS1991

The volcanic record that gets away

Volcanologists are accustomed to looking at the record in the rocks to read volcanic history. They map the extent of airfalls, the thickness and distribution of ignimrites and mudflows, and the nature and extent of lava flows. From these data they infer the story of previous eruptive episodes that are a key to what we may expect in the future. BUt some important volcanic events are not recorded. Without observations at present-day active volcanoes we would know little about the volcanic gas emitted, the kidns of gases, or the volume and the extent o the gas cloud.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Volcano hazard mitigation program in Indonesia

Volcanological investigations in Indonesia were started in the 18th century, when Valentijn in 1726 prepared a chronological report of the eruption of Banda Api volcno, Maluku. Modern and intensive volcanological studies did not begin until the catastrophic eruption of Kelut volcano, East Java, in 1919. The eruption took 5,011 lives and destroyed thousands of acres of coffee plantation. An eruption lahar generated by the crater lake water mixed with volcanic eruptions products was the cause of death for a high number of victims. An effort to mitigate the danger from volcanic eruption was first initiated in 1921 by constructing a tunnel to drain the crater lake water of Kelut volcano. At the same time a Volcanological Survey was established by the government with the responsibility of seeking every means for minimizing the hazard caused by volcanic eruption.

Earthquakes & Volcanoes (USGS)↗
USGS1993

Volcanic gases create air pollution on the Island of Hawai’i

In a handful of molten magma weighing about a pound, there is less than a tenth of an ounce, by weight, of idssolved gas-roughly the same weight as a pinch of table salt. Yet this tiny amount of gas produces spectacular lava foundations hundreds of meters high (see accompanying photograph). The fountain occurs as magma reaches the surface, because dissolved volcanic gases exolve and expand tremendously as pressure on the magma is released. Anyone who has shaken a bottle of soda and opened it quickly has received the full value of this basic principle of physics. Gases are dissolved in magma at depth, where pressures within Earth's crust are very great-many thousands of pounds per square inch. As the magma rises to the surface and erupts, the pressure decreases, and gas is released. The main gases dissolved in magma are water vapor, carbon dioxide, and sulfur gases, with lesser amounts of others, such as hydrogen, carbon monoxide, hydrochloric acid, and hydrofluoric acid. In our pinch-of-salt-to-a-handful-of-magma illustration above, most of the "pinch" is water vapor, followed by lesser amounts of carbon dioxide and sulfur gases with a few "grains" of hydrogen and other acid gases. The current eruption of Kilauea produces large quantities of volcanic gases that contribute to "volcanic air pollution." In this article we discuss the nature of the gases released from Kilauea, hoe we study them, and what happened to the gases in the environment after they are released.

Hawaii↗
USGS1993

Seismic detection of tornadoes

Tornadoes represent the most violent of all forms of atmospheric storms, each year resulting in hundreds of millions of dollars in property damage and approximately one hundred fatalities. In recent years, considerable success has been achieved in detecting tornadic storms by means of Doppler radar. However, radar systems cannot determine when a tornado is actually in contact with the ground, expect possibly at extremely close range. At the present time, human observation is the only truly reliable way of knowing that a tornado is actually on the ground. However, considerable evidence exists indicating that a tornado in contact with the ground produces a significant seismic signal. If such signals are generated, the seismic detection and warning of an imminent tornado can become a distinct possibility.

Earthquakes & Volcanoes (USGS)↗
USGS1988

Scientific goals of the Parkfield earthquake prediction experiment

Several unique circumstances of the Parkfield experiment provide unprecedented opportunities for significant advances in understanding the mechanics of earthquakes. to our knowledge, there is no other seismic zone anywhere where the time, place, and magnitude of an impending earthquake are specified as precisely. Moreover, the epicentral region is located on continental crust, is readily accessible, and can support a range of dense monitoring networks that are sited either on or very close to the expected rupture surface. As a result, the networks located at Parkfield are several orders of magnitude more sensitive than any previously deployed for monitoring earthquake precursors (a preearthquake change in strain, seismicity, and other geophysical parameters). In this respect the design of the Parkfield experiment resembles the rationale for constructing a new, more powerful nuclear particle accelerator:in both cases increased capabilities will test existing theories, reveal new phenomena, and suggest new research directions.

Earthquakes & Volcanoes (USGS)↗
USGS1990

Perspectives on earthquake hazards in the New Madrid seismic zone, Missouri

A sequence of three great earthquakes struck the Central United States during the winter of 1811-1812 in the area of New Madrid, Missouri. they are considered to be the greatest earthquakes in the conterminous U.S because they were felt and caused damage at far greater distances than any other earthquakes in U.S history. The large population currently living within the damage area of these earthquakes means that widespread destruction and loss of life is likely if the sequence were repeated. In contrast to California, where the earthquakes are felt frequently, the damaging earthquakes that have occurred in the Easter U.S-in 155 (Cape Ann, Mass.), 1811-12 (New Madrid, Mo.), 1886 (Charleston S.C) ,and 1897 (Giles County, Va.- are generally regarded as only historical phenomena (fig. 1). The social memory of these earthquakes no longer exists. A fundamental problem in the Eastern U.S, therefore, is that the earthquake hazard is not generally considered today in land-use and civic planning. This article offers perspectives on the earthquake hazard of the New Madrid seismic zone through discussions of the geology of the Mississippi Embayment, the historical earthquakes that have occurred there, the earthquake risk, and the "tools" that geoscientists have to study the region. The so-called earthquake hazard is defined by the characterization of the physical attributes of the geological structures that cause earthquakes, the estimation of the recurrence times of the earthquakes, the estimation of the recurrence times of the earthquakes, their potential size, and the expected ground motions. the term "earthquake risk," on the other hand, refers to aspects of the expected damage to manmade strctures and to lifelines as a result of the earthquake hazard.

New Madrid seismic zone↗
USGS1993

The October 12, 1992, Dahshur, Egypt, Earthquake

Cairo and northeastern Egypt experienced a rare, damaging earthquake on October 12, 1992. The earthquake, which measured 5.9 on the Richter magnitude scale, was centered near the village of Dahshur, about 18 km south of Cairo. The computed hypocentral depth of the earthquake, about 25 km, is consistent with the fact that fault rupture associated with the earthquake did not reach the surface. Despite its relatively moderate size, the earthquake caused many casualties and heavy damage. These losses included more than 500 fatalities, more than 6,500 injuries, and about 8,300 damaged or destroyed buildings. The Foreign Broadcast Service estimated monetary losses directly attributable to the earthquake at $300 million. We were part of an international reconnaissance team that investigated the Dahsur earthquake. This article summarizes our findings and points out how even a relatively moderate sized earthquake can cause widespread damage and a large number of casualities.

Earthquakes & Volcanoes (USGS)↗
USGS1991

Reducing volcanic risk; are we winning some battles but losing the war?

Historically, significant advances in volcanology have been catalyzed by volcanic disasters or crises, reflecting the the simple fact that volcanoes seem to receive serious scientific and public attention only when they cause, or threaten to cause, trouble. For example, three deadly eruptions in 1902, Mount Pelee, Santa Maria, and Soufriere (St.Vincent), spurred the movement to establish permanent volcano observatories there. Profoundly impresses by the devastation cused by Mont Pelee, Thomas A. Jaggar, Jr. founded the Hawaiian Volcano Observatory (HVO) in 1912. Since then, studies conducted at HVO and new observatories have been pivotal in transforming the nascent science of volcanology into the multidisciplinary science that it is today.

Earthquakes & Volcanoes (USGS)↗